Up to the present, internal pipe repair methods have approached repairing leaks in generally three different ways. One strategy involves installing resin coated or thermo-set liners along the entire section of suspected leaking pipe. The liner is usually held in position by inversion tubes, or direct gas or fluid pressure. A second strategy relates to positioning fibrous, resin impregnated or ribbed liners over a more specific section of pipe. This method may use inflatable bladders or other methods to hold the liner in place until set and cure. A third strategy of internal pipe repair involves directly applying sealant via elastic inversion tubes, plugs, pigs, or flooding the entire pipe directly.
Referring to the first strategy as embodied by Woolstencroft, U.S. Pat. No. 6,837,273, a fibrous, resin laden liner is utilized to seal entire sections of leaking pipe or conduit. McGuire, U.S. Pat. No. 6,539,978, uses a thermo-set technique instead of resin cure to effect seal of a leaking pipe. In either case, entire sections of pipe need to be lined to seal the smaller leaking portion, and therefore, knowledge as to the exact leak position is not necessary. Though both methods deal with leaks in linear sections of pipe, they do not deal with multiple opening junctions or severe pipe offset. Also, proper pipe preparation is often critical for these applications.
A second strategy for internal pipe repair can be seen in Topf, Jr., U.S. Pat. No. 6,435,566 and Harrington, U.S. Pat. No. 6,619,886. Topf, Jr. utilizes an internal interlocking rib and band system that holds a flexible sleeve in place. Harrington uses a resin impregnated sleeve that is pressed in place by a heated inverted tube. Although these methods aren't hampered by the requirement to line an entire section of pipe to repair just a small leak section, they still do not address multiple opening junctions and require proper pipe preparation. Also, knowledge of exact leak location is necessary to properly position the sleeve.
Finally, a third strategy deals with flooding entire pipe sections with sealant i.e. Nakashin U.S. Pat. No. 4,244,895 or Humphreys, et al., U.S. Pat. No. 5,194,193. Whereas, Humphreys, et al.'s method uses wax as a reusable sealant, Nakashin's technique expends self-curing grout in which the excess must be discarded and the sealant inconsistently held in place by a non-reactive fluid. Even the effectiveness of Humpheys, et al's reusable wax method is limited by operating temperature, pressure, and fluid reactivity requirements of the sealed pipe. A more refined method by Iwasaki-Higbee, U.S. Pat. No. 6,416,692 utilizes inversion tubes to force sealant into pipe cracks and voids. Knowledge as to the exact leak position is not necessary with this inclusive strategy of flooding or sealing entire sections of suspect pipe. As with the earlier sealing methods, however, multiple opening junctions are not addressed and proper pipe preparation is critical.